1. Field of the Invention
The present invention relates to a process for producing a substrate for a liquid ejection head.
2. Description of the Related Art
As methods for forming a liquid supply port in a substrate for a liquid ejection head, a method of using drilling, laser beam machining or sand blasting, a method of forming a liquid supply port by anisotropic etching and a method of forming a liquid supply port by dry etching have been proposed. Among these methods, the method of forming the liquid supply port by the dry etching using an etching gas can form a liquid supply port of an almost vertical form, so that a chip size can be made smaller than the method of forming the liquid supply port by the anisotropic etching. Regarding the method of forming the liquid supply port by the dry etching, Japanese Patent Application Laid-Open No. 2009-137155 discloses a process in which a common liquid supply port is formed from the side of a back surface of a substrate, and an independent liquid supply port is then formed in a bottom thereof by dry etching.